tidyxl: Read Untidy Excel Files

Imports non-tabular from Excel files into R. Exposes cell content,
position and formatting in a tidy structure for further manipulation.
Tokenizes Excel formulas. Supports '.xlsx' and '.xlsm' via the embedded
'RapidXML' C++ library <http://rapidxml.sourceforge.net>. Does not support
'.xlsb' or '.xls'.